cmd/vnet: omit log spam when backend status hasn't changed

Updates #13038

Change-Id: I9cc67cf18ba44ff66ba03cda486d5e111e395ce7

cmd/vnet/vnet-main.go

@@ -89,6 +89,7 @@ func main() {
 		http.ListenAndServe(":8080", rp)
 	}()
 	go func() {
+		var last string
 		getStatus := func() {
 			ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
 			defer cancel()
@@ -97,8 +98,11 @@ func main() {
 				log.Printf("NodeStatus: %v", err)
 				return
 			}
+			if st.BackendState != last {
+				last = st.BackendState
 				log.Printf("NodeStatus: %v", logger.AsJSON(st))
 			}
+		}
 		for {
 			time.Sleep(5 * time.Second)
 			//continue